The long-term goal of this project is to develop prosthetic foot technology that can function differently for walking and standing tasks. Although current prostheses can be very effective for particular tasks (e.g. walking, running, or standing), an amputee must often choose a single prosthesis to achieve reasonably good performance across all daily activities. This results in a compromise, because the biomechanical demands of walking are different from those for standing. Because walking and standing are two of the most common functional tasks performed daily, a dual function prosthetic foot could switch between two biomechanical modes of behavior. The proposed biomechanical behaviors include different foot bottom shapes and stiffnesses for walking and standing. During walking, the foot effectively rolls over the ground, in a motion that is facilitated by a convex foot bottom shape. During standing, a stable base of support is needed, which is facilitated by a concave foot bottom shape. The ideal stiffness for each task also depends on the differing demands of dynamic and static stability. Based on studies of gait mechanics, both shape and stiffness should be adjusted for the task. The Specific Aims of this project are to: 1.To design and construct a prosthetic foot prototype with separate modes for walking and standing under computer control based on the user's activity, and test its mechanical characteristics such as stiffness, adjustability, and fast mode switching. 2. To perform proof-of-concept testing of the prototype prosthetic foot's effect on walking and standing in amputees. PUBLIC HEALTH RELEVANCE: The two most common mobility issues for lower limb amputees are discomfort and fatigue. Persons wearing prosthetic feet find it uncomfortable to stand for long periods or to walk more than moderate distances. These issues are in part due to the fact that walking and standing have different biomechanical demands, which must be addressed by a single prosthetic foot. We propose to develop a computer-controlled prosthetic foot that can switch between different biomechanical characteristics depending on the user's task. The prosthetic foot is intended to improve stability for standing, and reduce impact forces on the leg during walking, and to automatically switch between characteristics during daily life. Such technology may improve comfort and reduce fatigue for amputees.